Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$189.36	5.851%	$200.4395	$200.44	$200.45	$200.40
Purchase #2	$239.72	7.816%	$258.4565	$258.46	$258.45	$258.50
Purchase #3	$241.47	13.458%	$273.967	$273.97	$273.95	$274.00
Purchase #4	$81.29	11.166%	$90.3668	$90.37	$90.35	$90.40
Purchase #5	$27.64	7.220%	$29.6356	$29.64	$29.65	$29.60
Purchase #6	$186.73	6.187%	$198.283	$198.28	$198.30	$198.30
Purchase #7	$208.57	6.615%	$222.3669	$222.37	$222.35	$222.40
7 purchase totals =	$1,174.78		$1,273.5153	$1,273.53	$1,273.50	$1,273.60